驗證關聯對象

Question

的給定數量的：

class User < ActiveRecord::Base 
    has_many :photos 
    MAX_PHOTOS = 5 
    validate :quantity_of_photos 

    def quantity_of_photos 
    ??? 
    end 
end 

這：

@user.photos.size # => 5 

我需要這個失敗：

@user.photos << Photo.create(valid_photo_attributes) 

如何做到這一點的驗證？

Answer 1

移動照片的方法的數量在照片模式：

class Photo < ActiveRecord::Base 

    belongs_to :user 
    validates :quantity_of_photos 

    def quantity_of_photos 
     if new_record? && user.photos.size >= User::MAX_PHOTOS 
     errors.add_to_base "You cannot have more than #{MAX_PHOTOS} photos." 
     end 
    end 

end 

一個ActiveRecord的實例的有效性是由是否有它的錯誤陣列錯誤決定。